by PeteB » 19 May 2016, 05:24
by dunghnguyen » 19 May 2016, 06:46
by hondagx35 » 19 May 2016, 11:57
by PeteB » 19 May 2016, 14:46
by dunghnguyen » 20 May 2016, 10:56
by rikardo1979 » 20 May 2016, 11:34
by PeteB » 20 May 2016, 14:09
rikardo1979 wrote:.... All this is coming from your cable as its like an long aerial
by PeteB » 20 May 2016, 15:19
by rikardo1979 » 20 May 2016, 17:29
PeteB wrote:rikardo1979 wrote:.... All this is coming from your cable as its like an long aerial
Not in this case. You are correct about using good cables of course, but the noise is not RFI or EMI (I tested for that).
Here is why I know how the noise is being conducted by the HDMI cable:
If I disconnect the cable at either end, the noise goes away. Same result if I leave the cable connected and the TV (or monitor) turned on and plugged into the wall socket, and I simply turn off or unplug all possible noise sources. If the cable acted like an aerial, akin to an un-terminated scope probe for example, then some noise would remain if I left the cable connected to the pi, and disconnected at the TV. The noise would also change if I moved the cable, or if I made a loop and rotated it.
It is definitely noise from various sources, conducted over the HDMI cable and through the HDMI connector. I can induce varying amounts of noise. With all noise sources removed, the results are quite good.
With RMAA and a 24-bit sound card input, 0.004% THD and -100db A-weighted noise is at the limit of the hardware.
With calibrated inputs and better software, I can measure down to 0.002% THD (0.001% would be perfect score for the DAC+).
by PeteB » 20 May 2016, 20:19
- get new TV which dont push noise over HDMI - very expensive option
- dont use HDMI in HiFi - highly recommended
- dont use this measuring software, so you would not know (if the noise is not audible) - best solution